Things to look for are that they actually pay sufficient attention to your account.
That said, I do manage Adwords campaigns (I have the certificates). To be honest, I have done Adwords for years for myself, but I just started doing it also as a freelance. I have my first real client job going on right now. I can be hired through O-Desk, though I have company also. I can tell more and send some more details if you are interested.
I live in Europe (EU), I am not native English speaker, but I have set up Adwords campaigns for all biggest European countries and for USA. Mainstream campaigns to exact, as you asked for that.
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